Monitor of ammonia in dosing system

ABSTRACT

An ammonia dosing system has a canister whose interior contains ammonia luminophores and a delivery apparatus for delivering ammonia from the canister interior into an exhaust after-treatment system to entrain with engine exhaust flowing toward an SCR catalyst for catalytic conversion of NO x  in engine exhaust.

TECHNICAL FIELD

This disclosure relates to an ammonia dosing system which delivers ammonia in gas phase from an ammonia storage canister into exhaust for after-treatment of oxides of nitrogen (NO_(x)) in the exhaust by selective catalytic reduction (SCR).

BACKGROUND

Selective catalytic reduction (SCR) is an exhaust after-treatment technology for enabling certain chemical reactions to occur between oxides of nitrogen (NO_(x)) in exhaust and ammonia (NH₃) introduced in gas phase into an exhaust system upstream of an SCR catalyst to entrain with exhaust flowing toward the catalyst where catalytic reactions convert NO_(x) into Nitrogen (N₂) and water (H₂O).

A motor vehicle which uses SCR technology for after-treatment of engine exhaust produced by operation of an internal combustion engine carries an on-board supply of ammonia which is stored in one or more canisters. Such canisters are constructed to be removable from a vehicle, re-chargeable at a service facility, and re-installable in a vehicle.

Strontium chloride is an example of a storage medium which is present inside a canister for storing ammonia in solid phase and releasing stored ammonia in gas phase when heated to an ammonia release temperature.

Because selective catalytic reduction of NO_(x) cannot occur in the absence of ammonia, information about ammonia in an ammonia dosing system would be useful in avoiding potential loss or interruption of ammonia flow between an ammonia storage canister and in an exhaust system.

SUMMARY OF THE DISCLOSURE

This disclosure introduces apparatus and method for acquiring information about ammonia in an ammonia dosing system through the use of optically detectable ammonia.

Certain gases which are typically considered not optically detectable can be made optically detectable by certain processes. A process which creates what are called “fluorophore absorber pairs” in an ammonia molecule can render ammonia optically detectable. The fluorophore absorber pairs radiate absorbed energy at a characteristic wavelength.

A gas which has been rendered optically detectable may be said to luminesce or fluoresce. Although the terms “luminophore” and “fluorophore” are used in scientific literature as descriptors of molecules which are optically detectable, it appears that the latter is used to characterize certain species of the former. The process which creates fluorophore absorber pairs in an ammonia molecule suggests that the molecule is a fluorophore, a species of the generic descriptor “luminophore.” The present applicants will use the term “luminophore” here as a generic descriptor of an optically detectable molecule.

The apparatus and method disclosed here are useful in an ammonia dosing system which treats engine exhaust passing through an SCR after-treatment system using ammonia which contains ammonia luminophores.

The presence of ammonia luminophores in an ammonia dosing system provides luminescence of ammonia which renders the ammonia detectable by optical sensing apparatus.

Specific sensing capabilities of optical sensing apparatus are a function of specific optical sensing technique employed and can extend from merely distinguishing between the presence and the absence of ammonia to measuring ammonia quantity and/or ammonia flow.

Several embodiments of apparatus are disclosed.

The apparatus and method can reduce the likelihood that an ammonia storage canister which contains little or no ammonia being installed in a vehicle.

The apparatus and method can indicate quantity of ammonia present inside an ammonia storage canister.

The apparatus and method can indicate outflow of ammonia from an ammonia storage canister.

A general aspect of the disclosed subject matter relates to an internal combustion engine comprising an exhaust after-treatment system comprising an SCR catalyst, and an ammonia dosing system comprising a canister having an interior containing optically detectable ammonia and a delivery apparatus for delivering optically detectable ammonia from the canister interior into the exhaust after-treatment system to entrain with engine exhaust flowing toward the SCR catalyst for catalytic conversion of NO_(x) in the engine exhaust.

A monitor of ammonia luminophores comprises at least one optical sensor for detecting luminescence of ammonia luminophores in the ammonia dosing system.

The monitor comprises a device providing a signal distinguishing high luminescence of ammonia luminophores detected by the at least one optical sensor and low luminescence of ammonia luminophores detected by the at least one optical sensor.

The least one optical sensor provides a measure of luminescence of ammonia luminophores which the at least one optical sensor detects, and the monitor converts a measure of luminescence of ammonia luminophores which the at least one optical sensor detects into a quantified measure of ammonia.

The monitor provides a signal alert when a quantified measure of ammonia is less than a predetermined quantity.

The canister comprises a port via which the canister separably connects to the delivery apparatus, and the at least one optical sensor is arranged to view luminescence of ammonia luminophores within the canister's interior.

When the canister's port is connected to the delivery apparatus and the at least one optical sensor detects luminescence of ammonia luminophores greater than a predetermined luminescence, a closure is operated to allow ammonia flow between the canister interior and the exhaust after-treatment system. When the canister's port is connected to the delivery apparatus and the at least one optical sensor detects luminescence of ammonia luminophores less than the predetermined luminescence, the closure is operated to disallow ammonia flow between the canister interior and the exhaust after-treatment system.

In a disclosed embodiment, the closure and the at least one optical sensor are mounted on the delivery apparatus.

Another general aspect of the disclosed subject matter relates to a method for detection of ammonia in an ammonia dosing system which delivers ammonia into an engine exhaust after-treatment system to entrain with exhaust flowing toward an SCR catalyst for catalytic conversion of NO_(x). The method comprises: installing in the ammonia dosing system an ammonia storage canister which contains ammonia luminophores; operating the ammonia dosing system to deliver ammonia from the ammonia storage canister into the exhaust after-treatment system; and using at least one optical sensor to detect luminescence of ammonia luminophores in the ammonia dosing system.

The method comprises providing a signal distinguishing high luminescence of ammonia luminophores detected by the at least one optical sensor and low luminescence of ammonia luminophores detected by the at least one optical sensor.

The method comprises using a measure of luminescence of ammonia luminophores which the at least one optical sensor detects to quantify a measure of ammonia.

The method provides a signal alert when a quantified measure of ammonia is less than a predetermined quantity.

The method comprises arranging the at least one optical sensor to view luminescence of ammonia luminophores in the canister's interior and when the at least one optical sensor detects luminescence of ammonia luminophores greater than a predetermined luminescence, allowing ammonia flow between the canister interior and the exhaust after-treatment system, and when the at least one optical sensor detects luminescence of ammonia luminophores less than the predetermined luminescence, disallowing ammonia flow between the canister interior and the exhaust after-treatment system.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a general schematic diagram of an internal combustion engine which utilizes SCR to convert NO_(x) in engine exhaust by chemical reaction with ammonia introduced into the exhaust.

FIG. 2 is a schematic diagram showing more detail.

FIG. 3 is a schematic diagram similar to FIG. 2 but showing a different embodiment.

DETAILED DESCRIPTION

FIG. 1 shows a representative internal combustion engine 10 which can be used in stationary or mobile applications. For example, engine 10 may be a diesel engine of the type which propels a motor vehicle such as a truck and which comprises structure forming a number of engine cylinders 12 into which fuel is injected by fuel injectors 14 to combust with air which has entered combustion chamber spaces of engine cylinders 12 through an intake system 16 when cylinder intake valves 18 for controlling admission of air from an intake manifold 20 into respective engine cylinders 12 are open.

Engine 10 also comprises an exhaust system 22 through which engine exhaust created by combustion of injected fuel in the combustion chamber spaces to operate engine 10 is conveyed to atmosphere. Cylinder exhaust valves 24 control admission of exhaust from respective engine cylinders 12 into an exhaust manifold 26 for further conveyance through exhaust system 22.

Exhaust system 22 includes an exhaust after-treatment system 28, including an SCR catalyst 30 for treating exhaust passing through after-treatment system 28 prior to entry into the atmosphere. An ammonia dosing system 32 provides ammonia in gas phase for catalytic conversion of NO_(x) in the exhaust.

Ammonia dosing system 32 comprises at least one ammonia storage canister 34 and an ammonia dosing controller 36 for controlling delivery of ammonia through an ammonia delivery apparatus 38 into after-treatment system 28 and for monitoring ammonia in the ammonia dosing system.

FIG. 2 shows one of the storage canisters 34 to comprise a walled enclosure 40 having a port 42 at one axial end via which the canister separably connects to ammonia delivery apparatus 38.

Ammonia delivery apparatus 38 comprises a tubular conduit terminating is a fitting 44 to which port 42 separably connects. Fitting 44 contains at least one optical sensor 46 and a selectively positionable closure 48.

Canister 34 comprises an interior containing an ammonia storage medium 50 for storing ammonia in solid phase and releasing stored ammonia in gas phase when heated to an ammonia release temperature. The stored ammonia comprises ammonia luminophores in quantity sufficient to provide for detection by at least one optical sensor 46 even when ammonia remaining in canister 34 reaches a point calling for canister replacement. FIG. 2 shows at least one optical sensor 46 arranged to view luminescence of optically detectable ammonia within the canister's interior.

The at least one sensor 46 and any associated device or devices, such as a device 52, form a monitor 54 of ammonia luminophores. Specific sensing capabilities of a particular monitor 54 are a function of specific optical sensing technique employed. A monitor may have a capability extending beyond merely detecting the presence or absence of ammonia to a capability of measuring ammonia quantity and/or ammonia flow.

Device 52 functions to provide a signal distinguishing high luminescence of ammonia luminophores detected by the at least one optical sensor 46 and low luminescence of ammonia luminophores detected by the at least one optical sensor 46. Low luminescence includes no luminescence.

At least one sensor 46 which provides a measure of luminescence of ammonia luminophores which the at least one optical sensor 46 detects can enable monitor 54 to convert a measure of luminescence of ammonia luminophores which the at least one optical sensor 46 detects into a quantified measure of ammonia in canister 34.

Monitor 54 can provide a signal alert when a quantified measure of ammonia is less than a predetermined quantity. This is useful in signaling that ammonia in a canister presently in use is approaching depletion and that a fresh canister should be brought on line.

When port 42 is connected to fitting 44 so that at least one optical sensor 46 can detect luminescence of ammonia luminophores within the canister interior, and the detected luminescence is greater than a predetermined luminescence, ammonia dosing controller 36 positions closure 48 via an actuator (not shown) to allow ammonia flow between the canister interior and after-treatment system 28. When port 42 is connected to fitting 44 and at least one optical sensor 46 detects luminescence of ammonia luminophores less than the predetermined luminescence, ammonia dosing controller 36 positions closure 48 to disallow ammonia flow between the canister interior and the after-treatment system.

Because of the presence of at least one optical sensor 46 and closure 48 in association with ammonia dosing controller 36, the presence of ammonia in a newly installed canister will be verified by at least one sensor 46 detecting luminescence of ammonia luminophores within the interior of the canister and consequently ammonia dosing controller 36 operating closure 48 to allow flow. If the presence of ammonia in a newly installed canister is not verified, ammonia dosing controller 36 maintains closure 48 in the same closed position which it had assumed when the previous canister was disconnected from fitting 44 to disallow flow.

The embodiment of FIG. 3 differs from that of FIG. 2 in that the at least one sensor 46 and closure 48 are mounted on canister port 42 rather than on fitting 44. Both the least one sensor 46 and the actuator for operating closure 48 are to be connected to device 52 and ammonia dosing controller 36 as shown after port 42 has been connected to fitting 44. 

What is claimed is:
 1. An internal combustion engine comprising: an exhaust after-treatment system comprising an SCR catalyst; an ammonia dosing system comprising a canister having an interior containing ammonia luminophores and a delivery apparatus for delivering ammonia from the canister interior into the exhaust after-treatment system to entrain with engine exhaust flowing toward the SCR catalyst for catalytic conversion of NO_(x) in the engine exhaust.
 2. The internal combustion engine set forth in claim 1 including a monitor of ammonia luminophores comprising at least one optical sensor for detecting luminescence of ammonia luminophores in the ammonia dosing system.
 3. The internal combustion engine set forth in claim 2 in which the monitor comprises a device providing a signal distinguishing high luminescence of ammonia luminophores detected by the at least one optical sensor and low luminescence of ammonia luminophores detected by the at least one optical sensor.
 4. The internal combustion engine set forth in claim 2 in which the at least one optical sensor provides a measure of luminescence of ammonia luminophores which the at least one optical sensor detects, and the monitor converts a measure of luminescence of ammonia luminophores which the at least one optical sensor detects into a quantitative measure of ammonia.
 5. The internal combustion engine set forth in claim 4 in which the monitor provides a signal alert when a quantified measure of ammonia is less than a predetermined quantity.
 6. The internal combustion engine set forth in claim 2 in which the canister comprises a port via which the canister separably connects to the delivery apparatus, and the at least one optical sensor is arranged to view luminescence of ammonia luminophores within the canister's interior.
 7. The internal combustion engine set forth in claim 6 including a closure which, when the canister's port is connected to the delivery apparatus and the at least one optical sensor detects luminescence of ammonia luminophores greater than a predetermined luminescence, allows ammonia flow between the canister interior and the exhaust after-treatment system, and which, when the canister's port is connected to the delivery apparatus and the at least one optical sensor detects luminescence of ammonia luminophores less than the predetermined luminescence, disallows ammonia flow between the canister interior and the exhaust after-treatment system.
 8. The internal combustion engine set forth in claim 7 in which the closure and the at least one optical sensor are mounted on the delivery apparatus.
 9. A method for detection of ammonia in an ammonia dosing system which delivers ammonia into an engine exhaust after-treatment system to entrain with exhaust flowing toward an SCR catalyst for catalytic conversion of NO_(R), the method comprising: installing in the ammonia dosing system an ammonia storage canister which contains ammonia luminophores; operating the ammonia dosing system to deliver ammonia from the ammonia storage canister into the exhaust after-treatment system; and using at least one optical sensor to detect luminescence of ammonia luminophores in the ammonia dosing system.
 10. The method set forth in claim 9 comprising providing a signal distinguishing high luminescence of ammonia luminophores detected by the at least one optical sensor and low luminescence of ammonia luminophores detected by the at least one optical sensor.
 11. The method set forth in claim 9 comprising using a measure of luminescence of ammonia luminophores which the at least one optical sensor detects to quantify a measure of ammonia.
 12. The method set forth in claim 11 including providing a signal alert when a quantified measure of ammonia is less than a predetermined quantity.
 13. The method set forth in claim 9 comprising arranging the at least one optical sensor to view luminescence of ammonia luminophores in the canister's interior and when the at least one optical sensor detects luminescence of ammonia luminophores greater than a predetermined luminescence, allowing ammonia flow between the canister interior and the exhaust after-treatment system, and when the at least one optical sensor detects luminescence of ammonia luminophores less than the predetermined luminescence, disallowing ammonia flow between the canister interior and the exhaust after-treatment system. 